According to the United States Geological Survey (USGS), the earthquake that struck the eastern parts of Turkey on Sunday, October 23, had a magnitude of about 7.2. The event occurred at around 1:41 pm local time (10:41 UTC), and caught people completely off-guard.
The area in this NASA image focused just west of Lake Erçek, which is where the main tremor and most of its aftershocks occurred. According to Turkish authorities, the mountainous region in which the earthquake struck is close to the Iranian border.
This particular area is very geologically active, as it stands at a crossroads of tectonic plates, where the Arabian and Eurasian plates collide with and grind against each other. The Anatolian Block, on which this region is located, is trapped in the middle, and forced to move westwards.